Giving players skills in different languages is a good way to give a game world more verisimilitude. Especially if they are from different cultures or are different species (or some of them are robots). Relatively insular cultures like the elves and dwarves in most fantasy setting are unlikely to speak the common human languages amongst themselves, after all. And given the evidence of our own history, even among a single species you can have hundreds of languages within a comfortable horse-ride away.
The problem arises when characters don't share a common language. While amusing for a while, it quickly wears thin, as the players struggle to communicate with one another underneath the watchful eye of a GM who enforces the fact that they can't just talk. So eventually it devolves to the point where the mutual incomprehension is conveniently forgotten about.
The point is, really, to let the PCs share a way of communicating. It also avoids the pitfalls that occur when a player decides that, for once, he's not going to ignore the difficulties and decides to make something of it.
Obi-Wan: R4, contact the Jedi Council.
GM: He can't establish a link to Coruscant. There's some sort of interference.
R2-D2: Shame you don't have a droid with my superior capabilities.
Obi-Wan: Hmmm. Try Naboo, that's closer. I'll get Anakin to relay it.
GM: R4 opens a line Anakin and Padmé's ship, but it's on Tatooine.
[SFX]: < doop bebebloop >
GM: What was that, Pete?
R2-D2: R4 talks in beeps too, yes? So Obi-Wan can't understand what he's saying. I'm just making sure you get it right.
GM: Er... right. So, Anakin and Padmé aren't on board. R2, you get this call from Obi-Wan.
[SFX]: < squee whirr ping beedle bloop ding >
Obi-Wan: Great. I have to talk, via someone I can't understand, to someone I can't understand?
R2-D2: I'm just playing my character faithfully.
Obi-Wan: On second thought, maybe it's a blessing.